I’ve raised a price on an item, typically within one hour of posting if I feel I listed it too low.
I’m not sure what others’ strategies are, but I can see a few reasons:
1. At the time of listing, there are perhaps other similar listings that are priced lower. If they all sell and only one is left, perhaps the seller thinks they can make more money since there isn’t any more competition.
2. If it is a current model, perhaps manufacturers recently increased the retail price, making the used price also go up.